The present invention relates to a rectifier device and more particularly to majority carrier rectifier device for use in place of power rectifier diodes.
Advances toward smaller and more efficient power supplies are limited by the non-ideal characteristics of today's high-voltage power diodes. An ideal diode for high-voltage power applications would be characterized by a conduction state with zero forward voltage and a blocking state with unlimited voltage capability. Additionally the ideal diode would transition smoothly, in zero time, between the two states. Although a non-zero forward voltage drop and a finite reverse leakage current limits the efficiency of real diodes, other inherent characteristics limit the frequency at which they can be used. One way to decrease the size and weight of power supplies is to increase the rectification frequency. Therefore, the currently available high-voltage diodes are limiting the progress toward smaller power supplies.
The P-N junction diode and the Schottky barrier diode are the devices of choice for power applications. While both devices deviate from the ideal diode, the Schottky diode has a low reverse voltage capability and therefore, it is not suitable for high voltage applications. The P-N diode can blocking higher reverse voltages, but it does not transition smoothly from the conduction state to the blocking sate, thus it limits the rectification frequency of power supplies.
The P-N junction diode is a minority carrier device that requires a finite time to regain its blocking state after conduction. This finite time is the reverse recovery time required to deplete the minority carrier charge stored at the junction. During the reverse recovery interval, very large reverse currents flow because the minority carrier charge maintains the junction in the conduction state. The large reverse currents are a source of noise that must be attenuated to meet the electromagnetic interference (EMI) requirements of the power supply. The magnitude of the reverse current can be controlled by adding components to the external circuit. Yet this will result in a longer recovery interval and increased power dissipation. The reverse recovery interval degrades the performance of the power converter during a portion of the total rectification period. Therefore, as the frequency of rectification increases (and the period decreases) the P-N diode reverse recovery time will become a larger portion of the total rectification period. For a given set of noise and efficiency requirements the P-N junction diode will limit the frequency of operation of the power converter.
Schottky diodes are majority carrier devices, and so they do not have the same rectification frequency limitation as the P-N junction diodes. However, Schottky diodes are limited to low voltage applications. The reverse blocking voltage is a function of both the silicon doping and the physical thickness of the epitaxial and metallurgical junction layers. The epitaxial layer thickness and resistivity can be increased for higher voltage blocking capability, but only with an increase in forward voltage drop. It is this forward voltage versus reverse voltage breakdown tradeoff that has limited Schottky diodes to low voltage applications.
It is an object of the present invention to provide a rectifier for use in high frequency and high voltage power applications.
It is a further object of the present invention to provide a rectifier device that requires less complex snubbers and switching said networks when used in applications formerly using a fast recovery P-N diode.